The inventive concept relates to a semiconductor memory device. More particularly, the inventive concept relates to a magnetic memory device, and to a read method of reading data stored in a magnetic memory device.
Volatile semiconductor memories such as dynamic random access memories (DRAMs) are widely used as main memory components of electronic devices such as mobile handheld devices or computers. However, volatile semiconductor memories like DRAMs lose their stored data when power to the DRAM is removed.
On the other hand, a magnetic random access memory (MRAM) is a nonvolatile type of memory that overcomes the drawbacks of a DRAM being a volatile memory. Not only is a MRAM nonvolatile, but it may have high-integration, high-speed, and low-power consumption characteristics. Therefore, MRAMs are highly regarded as next-generation semiconductor memory devices.
In general, a magnetic memory cell of a MRAM has an access transistor that performs a switching operation and a magnetic tunnel junction (MTJ) element to store data. The MTJ element is a type of magnetic memory element including two ferromagnetic substances, and whose magneto resistance (MR) depends on the magnetization directions of the two ferromagnetic substances. That is, the magneto resistance of the MTJ element can be changed by changing the magnetization directions of the two ferromagnetic substances. In a memory cell of an MRAM, data stored by the MTJ element may be determined to be, or “read” as, ‘1’ or ‘0’ based on the level of magneto resistance.